autoperf cassini (cxi) nic performance counter module

[sudheerchunduri]

• rename the cassini nic performance counter module from apss to apcxi
• HPE uses the name libcxi for the cassini related libraries, so, the new name is consistent with that.
• PAPI interface is used to read the nic performance counters
• Limitation with PAPI interface - for nodes which contain multiple nics, only the counters from one nic can be read, there is no guarantee on the nic specific nic used because nic mapping can in principle allow traffic to go through multiple nics
• the topology discovery for slingshot topology is achieved through the xnodenames, hence the logic used here is very much system specific

[sudheerchunduri]

merge request into a wrong branch.